/**
  * Image Loader for the Moving Map Navigator Demonstrator Applet
  * @author Robert J Morton
  * @version 12 Dec 2007 
  * Extended for sandboxed jar-file operation Wed 01 Feb 2017 12:34:27 BRST */

import java.awt.Component;     // Java Abstract Windowing Toolkit
import java.awt.MediaTracker;  // for the new-fangled 1.1 event handling

public class imgldr {
  private movmap mm;             // instance reference to the movmap applet
  private msgpanel mp;           // instance reference for message panel
  private MediaTracker tracker;  // to track when the images have been loaded

  private boolean          // TRUE indicates:
    loadingImages = true,  // images are being loaded
    trackerError = false,  // tracker encountered an error
    loadFTT = true,        // erase and repaint of the loading message
    errorFTT = true;       // show load-error message

  imgldr(movmap mm, msgpanel mp) {
    this.mm = mm;  // instance reference to the movmap applet
    this.mp = mp;  // instance of message panel

    // create a media tracker and register images with it
    tracker = new MediaTracker(mm);

    if(mm.JarredImages) {  // load images from the applet's own jar file
      movmap.IMG1 = mm.getImage(getClass().getResource("clouds1.png"));
      movmap.IMG2 = mm.getImage(getClass().getResource("clouds2.png"));
      movmap.IMG3 = mm.getImage(getClass().getResource("clouds3.png"));
      movmap.IMG4 = mm.getImage(getClass().getResource("clouds4.png"));
    } else {               // load images directly from the remote server
      movmap.IMG1 = mm.getImage(mm.getDocumentBase(), "clouds1.png"); 
      movmap.IMG2 = mm.getImage(mm.getDocumentBase(), "clouds2.png"); 
      movmap.IMG3 = mm.getImage(mm.getDocumentBase(), "clouds3.png"); 
      movmap.IMG4 = mm.getImage(mm.getDocumentBase(), "clouds4.png"); 
    }
    /* Start a media tracker to monitor progress of the
    loading process for of each of the four image files. */

    tracker.addImage(movmap.IMG1,0);
    tracker.addImage(movmap.IMG2,0);
    tracker.addImage(movmap.IMG3,0);
    tracker.addImage(movmap.IMG4,0);
  }


  boolean awaitingImages() {

    if(loadFTT) {  // if this is the first time through here
      mp.showMsg("Loading images from server...", true, true);
      loadFTT = false;  // avoid repeating display every cycle      
    }

    /* Keep checking the tracker for a signal. If the tracker
    does not say anything, return without servicing the applet's
    thread. Drops through when tracker gives a completion signal */

    try { tracker.waitForAll(); } 
    catch(InterruptedException e){ return true; }
    return false;
  }


  // returns true when image loading has terminated loaded
  boolean imagesLoaded() {
    if(tracker == null) return true;

    if(loadingImages) {  // if image loading process still running

      // Get the status of the image loading process
      int ts = tracker.statusAll(false);

      // if loading process has completed, indicate image loading failure
      if((ts & MediaTracker.ERRORED) != 0) {
        trackerError = true;

        /* If this is the first pass through here,
        display the error message and set the flag
        to avoid repeated dispays of this message. */

        if(errorFTT) { 
          mp.showMsg("Error: couldn't load images.", false, true);
          errorFTT = false;
        }
      }
      /* If tracker has completed its task, clear flag
      to indicate that image loading has terminated. */

      if(ts == MediaTracker.COMPLETE)
        loadingImages = false;

    /* Else, the image loading process has just finished
    so refresh display if not already done. */

    } else {
      killTracker();
      mp.showMsg("Images Loaded.", true, true);
    }
    return false;
  }


  void killTracker() {

    /* If the tracker isn't already dead, remove (de-register)
    the images from it and then kill the tracker. */

    if(tracker != null) {
      tracker.removeImage(movmap.IMG1,0); 
      tracker.removeImage(movmap.IMG2,0);
      tracker.removeImage(movmap.IMG3,0); 
      tracker.removeImage(movmap.IMG4,0);
      tracker = null;
    }
  }


  boolean TrackerError(){return trackerError;}
}